1. Field of the Invention
The present invention relates to an internal combustion engine controlling apparatus for improving the accuracy and the reliability of controlling an internal combustion engine of a type that exhaust gas is circulated.
2. Discussion of Background
Generally, in the internal combustion engine of automobiles, controlling characteristics vary depending on operational conditions in the engine. Namely, there is change in controlled quantity such as an air-fuel ratio, ignition timing and so on when the revolution number N of the engine or a load L (such as air suction) is used as a parameter. Accordingly, it is necessary to control the controlled quantity such as ignition timing with high accuracy depending on operational conditions in the engine in order to efficiently run the engine. For this, when a micro-computer or a similar device is used, data on the controlled quantity (such as ignition lead-angle values) corresponding to the number of revolution N or load data L are stored in an ROM (read-only memory). As an example of the above-mentioned, Japanese Unexamined Patent Publication 68931/1973 discloses that the number of revolution N and load data L are memorized in the ROM as a table of a quadratic coordinate so that ignition timing for the engine is controlled on the basis of the data obtained by the table memory depending on the operational conditions of the engine.
In controlling an internal combustion engine provided with an exhaust gas recirculation device, the operational conditions of the engine change depending on an amount of exhaust gas to be recirculated. Accordingly, it is necessary to determine a controlled quantity such as ignition timing by adding data on the exhaust gas recirculation quantity. In this case, as data on the exhaust gas recirculation quantity, an amount of lifting the valve body of a control valve is used to control an amount of recirculation of the exhaust gas (hereinbelow, referred to as EGR). Or, a negative pressure of air to be supplied to a driving means is used when a negative pressure type actuator is used as a driving means for driving the control valve. Or a signal such as a driving current is used when an electric type actuator is used.
In order to obtain data on a controlled quantity such as ignition timing, the data of number of revolution N, a load L and the above-mentioned EGR are added as parameters, and the data stored in given locations in the memory are sequentially read in response to the operational conditions of the engine, whereby the controlled quantity such as the ignition timing is determined on the basis of the read data.
Generally, although detected values such as the number of revolution N and the load L (for instance, a negative pressure in an intake air system) do not substantially change with the lapse of time in the lifetime of engine, there is found a substantial change in detected values on the data E of the EGR when the value at the initial stage of use is compared with the value measured after a long time use because carbon in the exhaust gas deposits on an EGR control valve and on the wall of the duct when the engine is used for a long period. Accordingly, it is difficult to accurately control the engine because the detected values do not correspond to the actual operational conditions of the engine and because the initial value of the controlled quantity of the engine moves.